Question

how many atoms are in 80.45g of magnesium?

Answer 1

Convert mass to moles (divide by molar mass), then convert moles to number of atoms (multiply by Avogadro's number).

Answer 2

There is one mol per 24.305g of Mg.: \(80.45/24.305=??\)
Once you know the moles of the sample you can use Avagadro's number to find the number of atoms.
\(6.02× 10^23 × (??)=\)_______\(×10^24\) atoms of Mg

@hype.child Solving, how much you got ?